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  • PHP undefined index $_GET
    PHP undefined index $_GET
    The PHPUndefinedIndex:$_GET error is because the unpassed GET parameter key is accessed. The error occurs when trying to read a parameter that does not exist in the URL, for example using echo$_GET['id'] but the URL does not have?id=123. Avoiding methods include: 1. Use isset($_GET['id']) to determine whether the key exists; 2. Use the ternary operator to set the default value such as $id=isset($_GET['id'])? $_GET['id']:null; 3. Choose whether to use empty() or array_key_exists() according to your needs. Development suggestions include: not directly use unverified parameters and unification
    PHP Tutorial . Backend Development 779 2025-07-14 02:39:51
  • PHP undefined index after json_decode
    PHP undefined index after json_decode
    The problem with PHPundefinedindexafterjson_decode occurs mainly because of accessing non-existent keys. 1. Ensure that json_decode is executed correctly, check the JSON string format and use json_last_error() to determine whether the parsing is successful; 2. Use isset() or array_key_exists() to check whether it exists before accessing the key. The nested structure needs to be judged layer by layer; 3. Debug the output data structure through var_dump() or print_r() to confirm that the key name, hierarchy and type are correct; 4. Use the null merge operator?? to set the default value to avoid undefined index errors, improve code security and
    PHP Tutorial . Backend Development 230 2025-07-14 02:38:51
  • PHP convert ASCII value to character using chr
    PHP convert ASCII value to character using chr
    In PHP, using the chr() function can convert the ASCII value to the corresponding character. 1.chr() receives an integer parameter (ASCII code) and returns the corresponding characters; 2. The valid range is 0 to 127, and the results outside this range may vary from system to system; 3. Common uses include generating line breaks (chr(10)), carriage return (chr(13)), tab characters (chr(9)) and spaces (chr(32)); 4. Notes: Floating point numbers will be truncated, multi-byte characters need to be processed by mb_ function, and some ASCII codes have no visual output.
    PHP Tutorial . Backend Development 628 2025-07-14 02:38:10
  • php iterate over a date range
    php iterate over a date range
    It is recommended to use the DatePeriod class to traverse date ranges in PHP. 1. The DatePeriod class was introduced from PHP5.3, and date traversal is implemented by setting the start date, end date and interval. For example, generate a date list from 2024-01-01 to 2024-01-05, which does not include the end date by default; 2. If you need to include the end date, you can adjust the end date or set the INCLUDE_END_DATE parameter; 3. The manual loop method can also complete the traversal using the DateTime object and the modify() method, which is suitable for scenarios where step size needs to be flexibly controlled; 4. Pay attention to the time zone problem that should be explicitly set to avoid the system's default time zone affecting the result; 5. PHP automatically handles leap years
    PHP Tutorial . Backend Development 148 2025-07-14 02:37:50
  • PHP prepared statement example
    PHP prepared statement example
    Preprocessing statements can effectively prevent SQL injection and improve execution efficiency in PHP database operations. When inserting data using MySQLi, use prepare() to define the statement, bind_param() to bind parameters. After multiple executions, you only need to modify and change the variable and call execute(); when querying, use prepare() and bind_param() to pass parameters, and then bind the result variables through bind_result() and obtain data with fetch(); if PDO is used, similar functions can be achieved through named parameters and array parameters, such as prepare() and pass parameters with execute(), and pass parameters through fetch(PDO::FETCH_ASSOC
    PHP Tutorial . Backend Development 843 2025-07-14 02:36:21
  • What is Dependency Injection and why is it important in php development?
    What is Dependency Injection and why is it important in php development?
    DependencyInjection(DI)solvestightcouplinginPHPcodebyallowingexternalinjectionofdependencies,improvingflexibilityandtestability.Insteadofclassescreatingorlocatingtheirowndependencies,theyreceivethemfromoutside,makingiteasiertoswapimplementations,usem
    PHP Tutorial . Backend Development 560 2025-07-14 02:34:20
  • What is the difference between a function expression and a function declaration in PHP?
    What is the difference between a function expression and a function declaration in PHP?
    The main difference between function expressions and function declarations in PHP is to improve behavior and usage scenarios. Function declarations start with the function keyword, will be promoted and can be called before definition; suitable for scenarios where scripts are available anywhere, no conditional definition is required, and top-down readability is required. Function expressions assign functions to variables and will not be promoted. They must be defined first and then called; they are suitable for scenarios where conditions require the creation, use of closures or anonymous functions and are passed as parameters. The two are the same in terms of functional characteristics, but the creation and access timing are different.
    PHP Tutorial . Backend Development 470 2025-07-14 02:34:01
  • how to deep copy a php array
    how to deep copy a php array
    There are three ways to implement deep copy of arrays in PHP: First, use unserialize and serialize to disconnect references by serializing and deserializing, which is suitable for ordinary and nested arrays; second, object arrays combine clone and recursive functions to flexibly process mixed types but ensure that the class supports correct cloning; third, json_encode and json_decode are suitable for pure scalar data, with simple writing but no resources or special objects.
    PHP Tutorial . Backend Development 961 2025-07-14 02:24:20
  • PHP convert string to array
    PHP convert string to array
    String to arrays can be implemented in PHP in various ways. First, use the exploit() function to split the string according to the specified separator. The syntax is exploit(separator, string, limit). For example, separating the string with a comma will generate an array containing each element; second, if the string is in JSON format, json_decode($str,true) is used to parse it to obtain the array; third, when processing null values and whitespace characters, you can combine array_map('trim') to remove spaces on both sides of each element and filter empty items through array_filter(); fourth, if you need to control the number of splits, you can set it in explore().
    PHP Tutorial . Backend Development 615 2025-07-14 02:21:41
  • How to pass an associative array to a PHP function?
    How to pass an associative array to a PHP function?
    TopassanassociativearraytoafunctioninPHP,declarethefunctionwithaparametertoacceptanarray,accessitsvaluesusingkeys,checkforkeyexistencetoavoiderrors,optionallymodifythearraybyreferenceorreturnanewversion.1)Declarethefunctionnormally,expectinganarray;2
    PHP Tutorial . Backend Development 676 2025-07-14 02:16:41
  • How to parse a CSV string in PHP with str_getcsv
    How to parse a CSV string in PHP with str_getcsv
    How to parse CSV strings? Use the PHP built-in function str_getcsv() to parse CSV strings into arrays, supporting the setting of separators, wrappers and escape characters; when processing fields with quotes and line breaks, str_getcsv() can automatically recognize and parse correctly; the difference from fgetcsv() is that the latter is used for file reading, while str_getcsv() directly processes strings; in actual applications, you can first split multi-behavior arrays and then process them line by line, combining array_map and exploit to improve efficiency. If you need to associate the array, you can manually merge the title rows and data rows.
    PHP Tutorial . Backend Development 950 2025-07-14 02:13:20
  • PHP prepared statement get result
    PHP prepared statement get result
    The method of using preprocessing statements to obtain database query results in PHP varies from extension. 1. When using mysqli, you can obtain the associative array through get_result() and fetch_assoc(), which is suitable for modern environments; 2. You can also use bind_result() to bind variables, which is suitable for situations where there are few fields and fixed structures, and it is good compatibility but there are many fields when there are many fields; 3. When using PDO, you can obtain the associative array through fetch (PDO::FETCH_ASSOC), or use fetchAll() to obtain all data at once, so the interface is unified and the error handling is clearer; in addition, you need to pay attention to parameter type matching, execution of execute(), timely release of resources and enable error reports.
    PHP Tutorial . Backend Development 1005 2025-07-14 02:12:40
  • PHP addslashes and stripslashes explained
    PHP addslashes and stripslashes explained
    addslashesaddsbackslashestoquotesandspecificcharacters,whilestripslashesremovesthem.ThesefunctionsareusedforescapingstringsinPHPbuthavelimitedusecases.1.addslashespreventsissuesbyescapingquotesindynamiccontentlikeSQLqueriesorHTMLattributes.2.Itisusef
    PHP Tutorial . Backend Development 106 2025-07-14 02:05:10
  • php regex named capture groups
    php regex named capture groups
    Named capture groups are a feature in PHP regular expressions that improve code readability, which allows naming capture groups instead of using only numeric indexes. 1. The naming capture group is defined in syntax similar to (?...), making the code clearer and easier to maintain; 2. PHP's preg_match function supports this function and stores the results into an associative array, such as $matches['year']; 3. There are three equivalent writing methods for naming groups: (?...), (?'name'...), (?P...); 4. When applying, you should avoid duplicate naming, select meaningful names, use them in combination with preg_match_all, and are case-insensitive.
    PHP Tutorial . Backend Development 447 2025-07-14 02:00:37

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